Authentication, Authorization and Accounting Requirements for the Session Initiation Protocol

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1 Internet Engineering Task Force INTERNET-DRAFT draft-ietf-sipping-aaa-req-02.ps SIP WG J. Loughney, G. Camarillo Nokia, Ericsson February 5, 2003 Expires: August, 2003 Authentication, Authorization and Accounting Requirements for the Session Initiation Protocol Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as work in progress. To view the list Internet-Draft Shadow Directories, see Copyright Notice Copyright (c) The Internet Society (2003). All Rights Reserved. Abstract As SIP services are deployed on the Internet, there is a need for authentication, authorization and accounting of SIP sessions. This document sets out the basic requirements for this work. Contents 1 Introduction Terminology and Acronyms Requirements Language Requirements Common Requirements Communication within the same domain Communication between different domains Discovery Ability to Integrate Different Networks, Services and Users Updating SIP Server Entries Call Setup Times Security Authentication Requirements Authentication Based on SIP Requests Flexible Authentication of SIP requests Authorization Requirements

2 2.3.1 Ability to Authorize SIP Requests Information transfer Distribution of Profiles User De-authorization Accounting Requirements Separation of Accounting Information Accounting Information Related to Session Progression Accounting Information Not Related to Session Progression Support for One-Time and Session-based Accounting Records SIP Session Changes Support for Accounting on Different Media Components Support for Stateful and Stateless Accounting Configuration of Accounting Generation Parameters Support for Arbitrary Correlation IDs Support for Real-time and Non-Realtime Accounting Flexible Interface Scenarios WLAN Roaming Using Third Party Service Providers Simple 3GPP Example Security Considerations 8 5 Acknowledgements 8 6 Authors Addresses 9 1 Introduction The AAA working group is chartered to work on authentication, authorization and accounting solutions for the Internet. This work consists of a base protocol, applications, end-to-end security application and a general architecture for providing these services [3]. The AAA working group has specified applicability of AAA-based solutions for a number of protocols (e.g., AAA requirements for Mobile IP [4]). SIP is a signalling protocol for creating, modifying and terminating different types sessions such as Internet phone calls, multimedia distribution and multimedia conferences [1]. SIP sessions have needs for session authentication, authorization and accounting. In order to perform AAA, SIP entities need to access AAA information (e.g., check if the password provided by a user is correct or store accounting records related to a particular session). Rather than collocating a database with AAA information with every SIP entity in a network, it is desirable to have a common logical AAA server accessible by all the SIP entities. SIP entities use a SIP-AAA interface to access this AAA server. This document outlines some requirements on this SIP-AAA interface between SIP entities and AAA servers. This document is intended as a generic document for SIP AAA requirements. It does not intend to develop a charging and/or billing mechanism for SIP. One possible use of this document would be to create a basic AAA application for SIP needs. J. Loughney, G. Camarillo Expires August, 2003 [Page 2]

3 The protocol used in the SIP-AAA interface could be any protocol that meets the requirements outlined by this document. Possible candidates, among others, are Diameter and XML-based protocols following the web-services model. 1.1 Terminology and Acronyms AAA: Authentication, Authorization and Accounting Accounting: In this draft, accounting is meant in a broad sense, not simply charging or billing. Home AAA Server: Server where user with which the user maintains an account relationship. Online Accounting: Also known as real-time accounting. Downloading some kind of credit into the access device, and deducting from that credit as usage accumulates. Offline Accounting: Also known as non-realtime accounting. Transferring records to a home accounting server, for later billing and settlement, without doing any accounting-related control or feedback for the services rendered. SIP: Session Initiation Protocol UAC: User Agent Client UAS: User Agent Server Proxies: Proxies are nodes which forward requests and responses as well as make policy decisions. 1.2 Requirements Language In this document, the key words must, must not, required, shall, shall not, should, should not, recommended, may, and optional are to be interpreted as described in RFC 2119 [2]. 2 Requirements In this section, we list the requirements. It is assumed that different situations, deployment scenarios will affect which requirements are needed. It is not intended that all requirements need to be supported. Section 2.1 lists general requirements, Section 2.2 lists requirements related to authentication, Section 2.3 lists requirements related to authorization and Section 2.4 lists requirements related to accounting. 2.1 Common Requirements This section outlines general requirements on the SIP-AAA interface Communication within the same domain The SIP-AAA interface must support communications between a SIP entity and a AAA server that belong to the same domain. J. Loughney, G. Camarillo Expires August, 2003 [Page 3]

4 2.1.2 Communication between different domains The SIP-AAA interface must support communications between a SIP entity in one domain and a AAA server in another domain Discovery With the information contained in the SIP messages, the SIP-AAA interface must be able to deduct the particular AAA server that has to be queried Ability to Integrate Different Networks, Services and Users The basic AAA architecture must be access independent. Service providers have to be able to provide AAA services for SIP, irrespective of access method or technology Updating SIP Server Entries When required, the SIP-AAA interface must allow the AAA server to update the information about a user that a SIP entity has Call Setup Times AAA should not unduly burden call setup times where appropriate. It may be reasonable to support some delay during registration, but delay during sessions (especially real-time) are problematic Security AAA data MUST be able to be securely transported. The endpoints MUST be authenticated before data is sent. The endpoints MAY be authorized to access certain types of AAA data. 2.2 Authentication Requirements This section outlines requirements on the SIP-AAA interface related to authentication Authentication Based on SIP Requests The home AAA server MUST be able to authenticate a user based on any SIP request, except CANCEL. CANCEL is a hop-by-hop request that can be generated by proxies that do not have the user s credentials Flexible Authentication of SIP requests The scheme supported for the authentication between the SIP servers and the AAA infrastructure must be flexible enough to accommodate a variety of authentication mechanisms. In particular, the SIP-AAA interface must be able to accommodate all the authentication mechanisms mandated by the SIP specs. J. Loughney, G. Camarillo Expires August, 2003 [Page 4]

5 2.3 Authorization Requirements This section outlines requirements on the SIP-AAA interface related to authorization Ability to Authorize SIP Requests The SIP-AAA interface must allow AAA servers to authorize any SIP request, except CANCEL. CANCEL is a hop-by-hop request that can be generated by proxies. SIP servers receiving a CANCEL do not challenge it, as they would do with an end-to-end request. Instead, they check that the entity sending the CANCEL is the same as the one that generated the request being canceled Information transfer The SIP-AAA interface must allow transfering a wide range or set of information to be used to make an authorization decision Distribution of Profiles The SIP-AAA interface must allow a AAA server that is making an authorization decision to deliver the user profile to the SIP entity. Note that the user profile may provide further information about the authorization decision to the SIP entity. For instance, a SIP proxy receives an INVITE from user A addressed to user B. The SIP proxy queries a AAA server and gets the following answer: user A is authorized to call user B as long as the requests are routed through a particular SIP proxy server C. In this case, the SIP proxy needs to use SIP loose routing techniques to forward the INVITE so that it traverses SIP proxy C before reaching user B User De-authorization The SIP-AAA interface must allow the AAA server to inform a SIP entity when a particular user is no longer authorized to perform a particular task, even if it is an ongoing task. 2.4 Accounting Requirements This section outlines requirements on the SIP-AAA interface related to accounting. Accounting is more than simple charging. Accounting may be a simple list of services accessed, servers accessed, duration of session, etc. Charging for SIP sessions can be extremely complex and requires some additional study. It is not the intent of this section to focus on charging Separation of Accounting Information AAA accounting messages MUST be able to separate session duration information from other information generated via additional services (e.g., 3-way calling, etc.) Separating accounting information makes it possible to charge different parties for different aspects of the session Accounting Information Related to Session Progression There MUST be support in the SIP-AAA interface for accounting transfers where the information contained in the accounting data has a direct bearing on the establishment, progression and termination of a session. J. Loughney, G. Camarillo Expires August, 2003 [Page 5]

6 2.4.3 Accounting Information Not Related to Session Progression There MUST be support in the SIP-AAA interface for accounting transfers where the information contained in the accounting data does NOT have a direct bearing on the establishment, progression and termination of a session Support for One-Time and Session-based Accounting Records The SIP-AAA interface must allow SIP servers to provide relevant accounting information for billing and inter-network settlement purpose to the AAA servers. Both one-time event accounting records and session based (START, INTERIM, STOP records) accounting MUST be supported SIP Session Changes Accounting messages must be able to reflect changes in the SIP session that affects the charging of SIP session Support for Accounting on Different Media Components The SIP-AAA interface must support accounting per media component (e.g., voice and video). The SIP-AAA interface must enable different parties to be charged per media component Support for Stateful and Stateless Accounting Stateful and stateless accounting (also referred to as cumulative and non-cumulative accounting) must be supported by the SIP-AAA interface Configuration of Accounting Generation Parameters The SIP-AAA interface must allow AAA servers to communicate parameters for accounting generation Support for Arbitrary Correlation IDs Some networks need to be able to relate the accounting to some aspect of the session. Therefore, the SIP-AAA interface must support arbitrary correlation IDs Support for Real-time and Non-Realtime Accounting Real-time and Non-Realtime Accounting must be supported by the SIP-AAA Interface. Real-time accounting allows implementing credit-based charging, where an application checks the end user s account for coverage for the requested service event charge prior to execution of that service event (authorization) Flexible Interface The scheme supported for the accounting between the SIP servers and the AAA infrastructure must be flexible enough to accommodate a variety of accounting mechanisms. J. Loughney, G. Camarillo Expires August, 2003 [Page 6]

7 3 Scenarios This section outlines some possible scenarios for SIP and AAA interaction. These are purely illustrative examples, and do not impose any requirements. Figure 1 shows the typical call flow between a SIP proxy that communicates to a AAA server that performs authentication and authorization. All the examples are based on this flow. SIP SIP AAA UAC Proxy Server ---METHOD----> --Is it OK?--> <-----OK Figure 1: Call flow over the SIP-AAA interface The SIP proxy receives a request with certain credentials. The SIP UAC that generated the request may have included the credentials after having been challenged by the proxy using a 407 (Proxy Authentication Required) response. The SIP proxy sends a request to the AAA server asking if it is OK to provide a particular service for this request. The service may be simply routing forward the request or may consist of a more complex service. The AAA server checks that the credentials are correct (authentication), and checks the user profile. The user profile indicates that it is OK to provide the service, and responds to the SIP proxy. The SIP proxy provides the service requested by the SIP UAC. 3.1 WLAN Roaming Using Third Party Service Providers User A wants to establish a voice session over the Internet with user B. User A wants its SIP signalling to be routed through SIP proxy C, because it provides a call log service (i.e., SIP proxy C sends an to user A once a month with the duration of all the calls made during the month.) User A accesses the Internet using a WLAN access outside his home domain. User A, user B, SIP proxy C and the home AAA server of user A are all in different domains. SIP proxy C challenges the initial INVITE from user A with a 407 (Proxy Authentication Required) response, and user A reissues the INVITE including his credentials. SIP proxy C consults user s A home AAA server, which confirms that the credentials belong to user A and that SIP proxy C can go ahead and provide its service for that call. SIP proxy C routes the INVITE forward towards user B and sends an accounting message to the AAA server, which will be used later to charge user A for the service provided by SIP proxy C. J. Loughney, G. Camarillo Expires August, 2003 [Page 7]

8 SIP AAA User A Proxy C Server User B ----INVITE-----> < ACK------> ----INVITE-----> ---Is this OK?--> <------OK INVITE > -Accounting msg-> Figure 2: WLAN roaming user 3.2 Simple 3GPP Example User A is not in his home domain, but it still uses SIP proxy C, which is in user s A home domain, as the outbound proxy for an INVITE. SIP proxy C consults the home AAA server, which indicates that requests from user A have to be routed through SIP proxy D. SIP proxy C uses SIP loose routing so that the INVITE traverses D before reaching its destination. SIP proxy D will provide call log service for user A. The example in figure 3 illustrates roughly how a SIP based 3GPP network works. 4 Security Considerations This document is informational in nature, so it does not directly affect the security of the Internet. However, security is a basic requirement of this work. 5 Acknowledgements The authors would like to thank the participants of the SIP interim meeting, May 2002 for their comments. The authors would also thank Harri Hakala, Mary Barns, Pete McCann and Henry Sinnreich for their comments. The authors would like to thank the authors of the AAA Requirements for IP Telephony/Multimedia draft, which some of the information in this document is based on. J. Loughney, G. Camarillo Expires August, 2003 [Page 8]

9 SIP AAA SIP User A Proxy C Server Proxy D ----INVITE-----> < ACK------> ----INVITE-----> Is this OK?----> <-OK if routed thru D INVITE > 6 Authors Addresses John Loughney Nokia Research Center Itmerenkatu Helsinki Finland electronic mail: john.loughney@nokia.com Gonzalo Camarillo Ericsson Advanced Signalling Research Lab. FIN Jorvas Finland electronic mail: Gonzalo.Camarillo@ericsson.com Normative References Figure 3: 3GPP example [1] J. Rosenberg, H. Schulzrinne, G. Camarillo, A. R. Johnston, J. Peterson, R. Sparks, M. Handley, and E. Schooler, SIP: session initiation protocol, RFC 3261, Internet Engineering Task Force, June [2] S. Bradner, Key words for use in rfcs to indicate requirement levels, RFC 2119, Internet Engineering Task Force, Mar J. Loughney, G. Camarillo Expires August, 2003 [Page 9]

10 Informative References [3] P. Calhoun et al., AAA problem statements, internet draft, Internet Engineering Task Force, Nov Work in progress. [4] S. Glass, T. Hiller, S. Jacobs, and C. E. Perkins, Mobile IP authentication, authorization, and accounting requirements, RFC 2977, Internet Engineering Task Force, Oct The IETF takes no position regarding the validity or scope of any intellectual property or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; neither does it represent that it has made any effort to identify any such rights. Information on the IETF s procedures with respect to rights in standards-track and standards-related documentation can be found in BCP-11. Copies of claims of rights made available for publication and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementors or users of this specification can be obtained from the IETF Secretariat. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights which may cover technology that may be required to practice this standard. Please address the information to the IETF Executive Director. Full Copyright Statement Copyright (c) The Internet Society (2003). All Rights Reserved. This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of developing Internet standards in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English. The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assigns. This document and the information contained herein is provided on an AS IS basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. J. Loughney, G. Camarillo Expires August, 2003 [Page 10]